This invention relates, in one instance, to measuring the quantity or concentration of cells in a biological sample. The invention is useful in anatomic pathology, which is a medical and laboratory specialty that makes diagnoses on findings in human tissues and cells.
More broadly, the invention provides a method and apparatus for the controlled instrumented processing of particles with a filter device. The filter device is of the screen type, e.g. a membrane filter, that blocks particles of larger than a threshold size and passes smaller particles. The particles of interest are carried in a fluid, and a change in the flow of the liquid carrying the particles, due to blockage of the filter device by the particles, provides information of interest both regarding the blockage of the filter and regarding the particles.
The invention thus provides quantitative instrumentation information regarding particles, generally of unknown particles, by an indirect technique that measures a flow condition of a screen-type filter device in the flow path of a fluid that carries the particles.
One application of the invention is in the pathological test, termed a Pap smear test, that examines cells for the presence of cancer. An established procedure for this test transfers a measured quantity of cells from a biological sample to a microscope slide for examination. One prior procedure for obtaining the desired measured quantity of cells from the sample employs a flow cytometer, such as a Coulter counter. Another prior cell-counting procedure employs a photometric technique in which light is directed through a fluid-suspension of the cells. Photodetectors responsive to the resultant scattered light provide signals that are a measure of the quantity of cells in the suspension.
These known cytological procedures for quantizing cells have drawbacks, including requiring expensive equipment and having limited performance in terms of reliability, repeatability, accuracy and precision. They also present biohazard risks, including from the handling of biosamples.
It is accordingly an object of this invention to provide an improved method and apparatus for quantizing cells and other particles carried in a fluid medium. Specific objects are to provide such a method and apparatus for implementation at a relatively low cost, and for controllable automated operation with relatively high reliability, repeatability, accuracy and precision.
Other objects of the invention are to provide an improved method and apparatus for collecting a selected quantity of cells and other particles that are carried in a fluid medium, particularly in a liquid medium.
It is also an object of the invention to provide an improved method and apparatus for determining a quantitative measure of the flow condition of a screen-type filter device subject to obstruction by particles larger than a known threshold size.
Another object of the invention is to provide an improved method and apparatus for collecting a specified sample of cells for cytological examination.
Other objects of the invention will in part be obvious and will in part appear hereinafter.